FBI closes anthrax case, says scientist was killer

Wrapping up one of its most vexing investigations, the FBI concluded that Army scientist Bruce Ivins acted alone in the 2001 anthrax mailings that killed five people and further unnerved a nation still reeling from the 9/11 attacks.

The agency formally closed the case Friday, ending the long, frustrating hunt for the killer after years of false leads, no arrests and public criticism.

Ivins killed himself in 2008 as prosecutors prepared to indict him for the attacks. He had denied involvement, and his family and some friends have continued to insist he was innocent.

Many details of the case have already been disclosed, but newly released FBI documents paint a fuller portrait of Ivins as a troubled researcher whose life's work was teetering toward failure at the time the letters laced with anthrax were sent. As the U.S. responded to the mailings, that work was given new importance by the government, and he was even honored for his efforts on anthrax.

The documents also describe what investigators say was Ivins' bizarre, decades-long obsession with a sorority. The anthrax letters were dropped in a mailbox near the sorority's office in Princeton, N.J.